K. C. Le, Saga Bergqvist, Jonatan Henriksson, Per-Erik Bengtsson
In this study, Raman spectroscopy has been used to evaluate the evolution of the structural modification of soot during oxidation processes at various preset temperatures up to 700 °C. Two types of well-characterized mini-CAST soot, representing black soot and brown soot, were examined. The major difference between the signals from the two types of soot was the higher photoluminescence (PL) signal for brown soot compared with black soot, in addition to some variations in the first-order Raman signatures such as oxygenated groups and their evolutions during thermal oxidation treatment. An interesting observation was the increase in the PL signal for brown soot at increasing temperatures up to 150 °C probably due to the formation of small oxidized polycyclic aromatic hydrocarbon and defects, followed by a decrease in the PL signal until the soot was fully oxidized. We also demonstrated that brown soot is prone to oxidation in ex situ measurements, a factor that should be considered in the Raman analysis of soot.
在这项研究中，拉曼光谱被用来评估煤烟在高达 700 °C 的各种预设温度下氧化过程中结构改性的演变情况。研究了两种特性良好的微型 CAST 烟尘，分别代表黑色烟尘和棕色烟尘。两类烟尘信号的主要区别是棕色烟尘的光致发光（PL）信号高于黑色烟尘，此外，一阶拉曼特征（如含氧基团及其在热氧化处理过程中的演变）也存在一些差异。一个有趣的观察结果是，当温度升高到 150 ℃ 时，褐煤烟尘的聚光信号会增加，这可能是由于形成了小的氧化多环芳烃和缺陷，随后聚光信号会下降，直到烟尘完全氧化为止。我们还证明，在原位测量中，褐煤烟尘很容易被氧化，这是在对煤烟进行拉曼分析时应该考虑的一个因素。
{"title":"Observation of Structural Changes during Oxidation of Black and Brown Soot Using Raman Spectroscopy","authors":"K. C. Le, Saga Bergqvist, Jonatan Henriksson, Per-Erik Bengtsson","doi":"10.3390/c10020038","DOIUrl":"https://doi.org/10.3390/c10020038","url":null,"abstract":"In this study, Raman spectroscopy has been used to evaluate the evolution of the structural modification of soot during oxidation processes at various preset temperatures up to 700 °C. Two types of well-characterized mini-CAST soot, representing black soot and brown soot, were examined. The major difference between the signals from the two types of soot was the higher photoluminescence (PL) signal for brown soot compared with black soot, in addition to some variations in the first-order Raman signatures such as oxygenated groups and their evolutions during thermal oxidation treatment. An interesting observation was the increase in the PL signal for brown soot at increasing temperatures up to 150 °C probably due to the formation of small oxidized polycyclic aromatic hydrocarbon and defects, followed by a decrease in the PL signal until the soot was fully oxidized. We also demonstrated that brown soot is prone to oxidation in ex situ measurements, a factor that should be considered in the Raman analysis of soot.","PeriodicalId":503899,"journal":{"name":"C","volume":"76 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-04-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140702752","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
K. Lozovoy, V. Dirko, O. I. Kukenov, Arseniy S. Sokolov, Konstantin V. Krukovskii, Mikhail S. Snegerev, A. Borisov, Yury V. Kistenev, A. Kokhanenko
Two-dimensional silicon (silicene) and germanium (germanene) have attracted special attention from researchers in recent years. At the same time, highly oriented pyrolytic graphite (HOPG) and graphene are some of the promising substrates for growing silicene and germanene. However, to date, the processes occurring during the epitaxial growth of silicon and germanium on the surface of such substrates have been poorly studied. In this work, the epitaxial growth of silicon and germanium is studied directly during the process of the molecular beam epitaxy deposition of material onto the HOPG surface by reflection high-energy electron diffraction (RHEED). In addition, the obtained samples are studied by Raman spectroscopy and scanning electron microscopy. A wide range of deposition temperatures from 100 to 800 °C is considered and temperature intervals are determined for various growth modes of silicon and germanium on HOPG. Conditions for amorphous and polycrystalline growth are distinguished. Diffraction spots corresponding to the lattice constants of silicene and germanene are identified that may indicate the presence of areas of graphene-like 2D phases during epitaxial deposition of silicon and germanium onto the surface of highly oriented pyrolytic graphite.
{"title":"RHEED Study of the Epitaxial Growth of Silicon and Germanium on Highly Oriented Pyrolytic Graphite","authors":"K. Lozovoy, V. Dirko, O. I. Kukenov, Arseniy S. Sokolov, Konstantin V. Krukovskii, Mikhail S. Snegerev, A. Borisov, Yury V. Kistenev, A. Kokhanenko","doi":"10.3390/c10020036","DOIUrl":"https://doi.org/10.3390/c10020036","url":null,"abstract":"Two-dimensional silicon (silicene) and germanium (germanene) have attracted special attention from researchers in recent years. At the same time, highly oriented pyrolytic graphite (HOPG) and graphene are some of the promising substrates for growing silicene and germanene. However, to date, the processes occurring during the epitaxial growth of silicon and germanium on the surface of such substrates have been poorly studied. In this work, the epitaxial growth of silicon and germanium is studied directly during the process of the molecular beam epitaxy deposition of material onto the HOPG surface by reflection high-energy electron diffraction (RHEED). In addition, the obtained samples are studied by Raman spectroscopy and scanning electron microscopy. A wide range of deposition temperatures from 100 to 800 °C is considered and temperature intervals are determined for various growth modes of silicon and germanium on HOPG. Conditions for amorphous and polycrystalline growth are distinguished. Diffraction spots corresponding to the lattice constants of silicene and germanene are identified that may indicate the presence of areas of graphene-like 2D phases during epitaxial deposition of silicon and germanium onto the surface of highly oriented pyrolytic graphite.","PeriodicalId":503899,"journal":{"name":"C","volume":"23 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-04-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140716673","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Utilizing glucose as a targeting agent represents a pioneering approach in selectively directing nanoparticles towards cancer cells, capitalizing on the pronounced glucose uptake observed in tumors attributable to the Warburg effect. In this study, we have successfully adopted this targeting strategy to facilitate the specific uptake of advanced nanotools, comprising carbon nanocrystals incorporating gold seeds (AuCDs). Leveraging the advantageous optical and size-related properties of carbon nanodots in conjunction with gold-mediated X-ray attenuation capabilities, these hybrid nanomaterials have been engineered as contrast agents for a bi-modal imaging modality, exploiting the synergistic benefits of fluorescence imaging and X-ray computed tomography. Notably, for the synthesis of AuCDs, we present, for the first time, the incorporation of gold seeds within the molecular precursors of carbon nanodots during their solvothermal synthesis process, showcasing the efficacy of this synthetic pathway in yielding nanoscale carbon structures incorporating bioeliminable gold ultrasmall nanoparticles (d < 5 nm). Subsequently, we employed an azido-alkyne click chemistry reaction to functionalize the nanoparticle surface with 2-deoxy-D-glucose as a targeting moiety. The demonstrated cancer-targeting proficiency, as assessed via fluorescence imaging, renders the proposed nanosystem highly promising for a spectrum of applications in precision anticancer theranostics, encompassing both diagnostic and therapeutic endeavors.
利用葡萄糖作为靶向剂是将纳米粒子选择性地导向癌细胞的一种开创性方法，它充分利用了在肿瘤中观察到的可归因于沃伯格效应的明显葡萄糖摄取。在这项研究中，我们成功地采用了这种靶向策略，促进了先进纳米工具的特异性吸收，这些工具由包含金种子（AuCDs）的碳纳米晶体组成。利用碳纳米点的光学和尺寸相关特性以及金介导的 X 射线衰减能力，这些混合纳米材料被设计为双模态成像模式的造影剂，利用了荧光成像和 X 射线计算机断层扫描的协同优势。值得注意的是，在 AuCDs 的合成过程中，我们首次在碳纳米点的分子前体溶热合成过程中加入了金种子，展示了这种合成途径在生成包含生物可消除的金超小型纳米颗粒（d < 5 nm）的纳米级碳结构方面的功效。随后，我们采用叠氮-炔烃点击化学反应将纳米粒子表面的 2-脱氧-D-葡萄糖功能化为靶向分子。通过荧光成像评估，所展示的癌症靶向能力使所提出的纳米系统在精准抗癌治疗学的一系列应用中大有可为，其中包括诊断和治疗努力。
{"title":"Ultrasmall Glucose-Functionalized Au-Carbon Nanohybrids: Exploiting the Warburg Effect to Image Tumors by Multimodal CT/Fluorescence Imaging","authors":"Roberta Cillari, S. Scirè, G. Cavallaro, N. Mauro","doi":"10.3390/c10020035","DOIUrl":"https://doi.org/10.3390/c10020035","url":null,"abstract":"Utilizing glucose as a targeting agent represents a pioneering approach in selectively directing nanoparticles towards cancer cells, capitalizing on the pronounced glucose uptake observed in tumors attributable to the Warburg effect. In this study, we have successfully adopted this targeting strategy to facilitate the specific uptake of advanced nanotools, comprising carbon nanocrystals incorporating gold seeds (AuCDs). Leveraging the advantageous optical and size-related properties of carbon nanodots in conjunction with gold-mediated X-ray attenuation capabilities, these hybrid nanomaterials have been engineered as contrast agents for a bi-modal imaging modality, exploiting the synergistic benefits of fluorescence imaging and X-ray computed tomography. Notably, for the synthesis of AuCDs, we present, for the first time, the incorporation of gold seeds within the molecular precursors of carbon nanodots during their solvothermal synthesis process, showcasing the efficacy of this synthetic pathway in yielding nanoscale carbon structures incorporating bioeliminable gold ultrasmall nanoparticles (d < 5 nm). Subsequently, we employed an azido-alkyne click chemistry reaction to functionalize the nanoparticle surface with 2-deoxy-D-glucose as a targeting moiety. The demonstrated cancer-targeting proficiency, as assessed via fluorescence imaging, renders the proposed nanosystem highly promising for a spectrum of applications in precision anticancer theranostics, encompassing both diagnostic and therapeutic endeavors.","PeriodicalId":503899,"journal":{"name":"C","volume":"74 6","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-04-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140741675","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Our journal, C—Journal of Carbon Research (https://www.mdpi.com/journal/carbon), is an international, scientific, peer-reviewed, open access journal on carbon research, published quarterly online by MDPI [...]
我们的期刊《碳研究期刊》（C-Journal of Carbon Research，https://www.mdpi.com/journal/carbon）是一份国际性、科学性、同行评审、开放获取的碳研究期刊，由 MDPI [...] 在线出版，每季度一期。
{"title":"Editorial for C—Journal of Carbon Research in 2023","authors":"Craig E. Banks","doi":"10.3390/c10020034","DOIUrl":"https://doi.org/10.3390/c10020034","url":null,"abstract":"Our journal, C—Journal of Carbon Research (https://www.mdpi.com/journal/carbon), is an international, scientific, peer-reviewed, open access journal on carbon research, published quarterly online by MDPI [...]","PeriodicalId":503899,"journal":{"name":"C","volume":"50 7","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-04-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140755142","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
A. Tolkou, Konstantinos N. Maroulas, Dimitrios Theologis, I. Katsoyiannis, G. Kyzas
Wastewater treatment has attracted much attention in recent years as a potential source of water, and there are some concerns about its safety for human use. Eco-friendly and cost-effective adsorbent materials were successfully synthesized from several peels, such as orange, banana, pomegranate, avocado, kiwi, etc., and were used as natural adsorbents or as activated carbons derived from these peels for water and wastewater treatment. In this review, the latest research focusing on the effective modification of these peels for the removal of several pollutants found in wastewaters are summarized and compared, such as pharmaceuticals, dyes, heavy metals, and anions that are released in waste and have a negative impact on human and animal health. In this review, focus is given to activated carbon produced from fruit peels. Moreover, fruit peels as adsorbent materials, without previously being converted to activated carbon, are of limited use in the recent literature.
{"title":"Comparison of Modified Peels: Natural Peels or Peels-Based Activated Carbons for the Removal of Several Pollutants Found in Wastewaters","authors":"A. Tolkou, Konstantinos N. Maroulas, Dimitrios Theologis, I. Katsoyiannis, G. Kyzas","doi":"10.3390/c10010022","DOIUrl":"https://doi.org/10.3390/c10010022","url":null,"abstract":"Wastewater treatment has attracted much attention in recent years as a potential source of water, and there are some concerns about its safety for human use. Eco-friendly and cost-effective adsorbent materials were successfully synthesized from several peels, such as orange, banana, pomegranate, avocado, kiwi, etc., and were used as natural adsorbents or as activated carbons derived from these peels for water and wastewater treatment. In this review, the latest research focusing on the effective modification of these peels for the removal of several pollutants found in wastewaters are summarized and compared, such as pharmaceuticals, dyes, heavy metals, and anions that are released in waste and have a negative impact on human and animal health. In this review, focus is given to activated carbon produced from fruit peels. Moreover, fruit peels as adsorbent materials, without previously being converted to activated carbon, are of limited use in the recent literature.","PeriodicalId":503899,"journal":{"name":"C","volume":"28 5","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-03-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140081047","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
G. Ruscica, Fabio Peinetti, I. Natali Sora, Patrizia Savi
Biochar (bio-charcoal) is a low-cost and eco-friendly material. It can be obtained by thermochemical conversion of different biomass sources, for example, in the total absence of oxygen (pyrolysis) or in oxygen-limited atmosphere (gasification). The porous carbonaceous structure of biochar, resulting from the thermal treatment, can be exploited in cement-based composite production. By introducing biochar powder or other fillers in the cement paste, it is possible to enhance the shielding properties of the cement paste. The environmental impact of polyvinyl chloride (PVC) can be reduced by reusing it as a filler in cement-based composites. In this work, cement-based composites filled with different percentages of biochar and PVC are fabricated. The scattering parameters of samples with 4mm thickness are measured by mean of a rectangular waveguide in the C-band. The shielding effectiveness of reference samples without any filler and samples with biochar and PVC is analyzed. A combination of 10 wt.% biochar and 6 wt.% PVC provides the best shielding performance (around 16 dB).
{"title":"Analysis of Electromagnetic Shielding Properties of Cement-Based Composites with Biochar and PVC as Fillers","authors":"G. Ruscica, Fabio Peinetti, I. Natali Sora, Patrizia Savi","doi":"10.3390/c10010021","DOIUrl":"https://doi.org/10.3390/c10010021","url":null,"abstract":"Biochar (bio-charcoal) is a low-cost and eco-friendly material. It can be obtained by thermochemical conversion of different biomass sources, for example, in the total absence of oxygen (pyrolysis) or in oxygen-limited atmosphere (gasification). The porous carbonaceous structure of biochar, resulting from the thermal treatment, can be exploited in cement-based composite production. By introducing biochar powder or other fillers in the cement paste, it is possible to enhance the shielding properties of the cement paste. The environmental impact of polyvinyl chloride (PVC) can be reduced by reusing it as a filler in cement-based composites. In this work, cement-based composites filled with different percentages of biochar and PVC are fabricated. The scattering parameters of samples with 4mm thickness are measured by mean of a rectangular waveguide in the C-band. The shielding effectiveness of reference samples without any filler and samples with biochar and PVC is analyzed. A combination of 10 wt.% biochar and 6 wt.% PVC provides the best shielding performance (around 16 dB).","PeriodicalId":503899,"journal":{"name":"C","volume":"79 5","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-03-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140085246","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Jesús Noé Rivera Olvera, Luis Hernández Maya, L. G. Diaz Barriga Arceo
In the present work, the synthesis and decomposition of low-dimensional materials from a Ni15Mo25W10C50 system produced by mechanical alloying was reported. During the milling process, the resultant phases were WMoC and NiC, and after sintering and quenching, MoNi3, WMo, Ni4W, WC, MoNi and Mo2C were found. The samples were analyzed by X-ray diffraction, scanning electron microscopy, and energy-dispersive X-ray spectroscopy. Nanotubes with the lengths ranging from 500 nm to 2 μm, spheres and novelty globular particles with sizes ranging from 40 to 600 nm as well as “petal-like” estructure were observed. The results revealed the formation of a microstructure with morphology similar to spinodal decomposition followed by a sequence of invariant reactions leading the production of modulated and novel branched structures. We proposes a theoretical mechanism of formation that is associated with the modulated structure observed after quenching.
{"title":"Novel Morphology for NiWMo Carbides Obtained by Mechanical Alloying and Quenching","authors":"Jesús Noé Rivera Olvera, Luis Hernández Maya, L. G. Diaz Barriga Arceo","doi":"10.3390/c10010011","DOIUrl":"https://doi.org/10.3390/c10010011","url":null,"abstract":"In the present work, the synthesis and decomposition of low-dimensional materials from a Ni15Mo25W10C50 system produced by mechanical alloying was reported. During the milling process, the resultant phases were WMoC and NiC, and after sintering and quenching, MoNi3, WMo, Ni4W, WC, MoNi and Mo2C were found. The samples were analyzed by X-ray diffraction, scanning electron microscopy, and energy-dispersive X-ray spectroscopy. Nanotubes with the lengths ranging from 500 nm to 2 μm, spheres and novelty globular particles with sizes ranging from 40 to 600 nm as well as “petal-like” estructure were observed. The results revealed the formation of a microstructure with morphology similar to spinodal decomposition followed by a sequence of invariant reactions leading the production of modulated and novel branched structures. We proposes a theoretical mechanism of formation that is associated with the modulated structure observed after quenching.","PeriodicalId":503899,"journal":{"name":"C","volume":"84 4","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-01-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139530494","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
In recent times, biochar has emerged as a promising and sustainable solution for COD reduction in wastewater treatment. This study explores the potential of chemically modified biochars as efficient adsorbents for the removal of organic contaminants, specifically oils, fats, and grease (OFG), from wool scouring wastewater. Proximate analysis revealed distinct properties among the biochars, with KOH-treated biochar demonstrating the most promising characteristics, including lower volatile matter, higher fixed carbon content, and reduced ash content, indicating a stable and carbon-rich structure. A meticulous examination of the KOH-treated biochar’s surface characteristics revealed the presence of elevated carbon and nitrogen content, complemented by an expansive surface area measuring 724.4 m2/g. This surface area was at least twice as extensive as that observed in the other post-treated biochar samples. The kinetic adsorption of COD and soluble COD was well fitted by the pseudo-first-order model, with equilibrium achieved in approximately 200 min. The KOH-treated biochar exhibited the highest equilibrium adsorption capacities for both COD and soluble COD in both Dorset wool (Dorset) and Bluefaced Leicester (BFL) wastewater, highlighting its efficacy in OFG removal. Despite these promising results, further research is needed to explore biochar’s surface characteristics, pore structure, and performance under diverse conditions, as well as its integration with existing treatment processes and potential for regeneration and reuse. This study contributes to advancing sustainable wastewater treatment methods using chemically modified biochars.
{"title":"Enhancing Organic Contaminant Removal from Wool Scouring Wastewater Using Chemically Modified Biochars","authors":"Simeng Li, Desarae Tasnady, Shannon Skelley, Blanca Calderon, Sherine Jiang","doi":"10.3390/c10010006","DOIUrl":"https://doi.org/10.3390/c10010006","url":null,"abstract":"In recent times, biochar has emerged as a promising and sustainable solution for COD reduction in wastewater treatment. This study explores the potential of chemically modified biochars as efficient adsorbents for the removal of organic contaminants, specifically oils, fats, and grease (OFG), from wool scouring wastewater. Proximate analysis revealed distinct properties among the biochars, with KOH-treated biochar demonstrating the most promising characteristics, including lower volatile matter, higher fixed carbon content, and reduced ash content, indicating a stable and carbon-rich structure. A meticulous examination of the KOH-treated biochar’s surface characteristics revealed the presence of elevated carbon and nitrogen content, complemented by an expansive surface area measuring 724.4 m2/g. This surface area was at least twice as extensive as that observed in the other post-treated biochar samples. The kinetic adsorption of COD and soluble COD was well fitted by the pseudo-first-order model, with equilibrium achieved in approximately 200 min. The KOH-treated biochar exhibited the highest equilibrium adsorption capacities for both COD and soluble COD in both Dorset wool (Dorset) and Bluefaced Leicester (BFL) wastewater, highlighting its efficacy in OFG removal. Despite these promising results, further research is needed to explore biochar’s surface characteristics, pore structure, and performance under diverse conditions, as well as its integration with existing treatment processes and potential for regeneration and reuse. This study contributes to advancing sustainable wastewater treatment methods using chemically modified biochars.","PeriodicalId":503899,"journal":{"name":"C","volume":"47 36","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-01-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139382216","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
We conducted a large set of ab initio density functional theory computations to model a variety of hammer-terminated graphene nanoflakes—finite counterparts of armchair graphene nanoribbons. We focused on the relationships among the length and width of the nanoflakes, the stoichiometry and the conformation of the hydrogen saturation of the caps, and the resulting electronic structure. The energetics and the thermodynamic stability of the nanoflakes were investigated as well. Based on this study, we provide a recipe for determining the most stable saturation of the dangling bonds at the caps, which is generally disregarded in theoretical studies, and we prove that this step is crucial for a reliable description of the electronic structure of these systems. Data analysis proved that flakes far from the most stable C–H pattern exhibited electronic properties that were typical of an unsaturated bonding structure. Based on thermodynamics, we also proved that, for any given flake, there was a well-defined hydrogen content and a conformation of H atoms at the caps, which were favored across a wide range of environmental conditions.
{"title":"Thermodynamic Stability and Electronic Properties of Graphene Nanoflakes","authors":"R. Soave, F. Cargnoni, M. I. Trioni","doi":"10.3390/c10010005","DOIUrl":"https://doi.org/10.3390/c10010005","url":null,"abstract":"We conducted a large set of ab initio density functional theory computations to model a variety of hammer-terminated graphene nanoflakes—finite counterparts of armchair graphene nanoribbons. We focused on the relationships among the length and width of the nanoflakes, the stoichiometry and the conformation of the hydrogen saturation of the caps, and the resulting electronic structure. The energetics and the thermodynamic stability of the nanoflakes were investigated as well. Based on this study, we provide a recipe for determining the most stable saturation of the dangling bonds at the caps, which is generally disregarded in theoretical studies, and we prove that this step is crucial for a reliable description of the electronic structure of these systems. Data analysis proved that flakes far from the most stable C–H pattern exhibited electronic properties that were typical of an unsaturated bonding structure. Based on thermodynamics, we also proved that, for any given flake, there was a well-defined hydrogen content and a conformation of H atoms at the caps, which were favored across a wide range of environmental conditions.","PeriodicalId":503899,"journal":{"name":"C","volume":"29 51","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-01-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139388713","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Jobair Al Rafi, Yu Kanda, Mitsuhiro Honda, Yo Ichikawa
The hybrid structure of Graphene and ZnO (Graphene/ZnO) is emerging as a novel material used to achieve the high performance of photocatalysis. In this study, we examined the ZnO characteristics that affect the photocatalytic activity of graphene/ZnO using a lamellar structure of graphene and ZnO thin films. Graphene samples were synthesized via chemical vapor deposition, and a typical wet process was applied to transfer them on sputter-deposited ZnO thin films with and without annealing. We confirmed that graphene-deposited ZnO demonstrated more efficient photocatalytic behavior toward the decomposition of methylene blue (as a model organic compound) with ordinary sputtered ZnO thin films. Again, ZnO thin films annealed at 1000 °C in an N2 gas atmosphere with graphene performed better than unannealed films. XRD analysis confirmed that pre-thermal treatment of a ZnO thin film promoted re-crystallization, which had less impact on the photocatalytic improvement. The attachment of graphene to the film is considered to contribute to the enhancement. Raman analysis revealed that the graphene coverage areas on the post-annealed ZnO increased by two times compared to that of an unannealed film where the unannealed film had a higher graphene layer. The results presented in this study demonstrate that an annealed ZnO thin film forms a better attachment with graphene, resulting in a larger graphene coverage area with fewer multilayers, which effectively improves the photocatalytic activity in composite structures.
石墨烯和氧化锌（Graphene/ZnO）的混合结构正在成为一种用于实现高性能光催化的新型材料。在本研究中，我们利用石墨烯和氧化锌薄膜的层状结构研究了影响石墨烯/氧化锌光催化活性的氧化锌特性。石墨烯样品是通过化学气相沉积合成的，然后采用典型的湿法工艺将其转移到经过或未经退火的溅射沉积氧化锌薄膜上。我们证实，与普通的溅射氧化锌薄膜相比，石墨烯沉积氧化锌在分解亚甲基蓝（作为模型有机化合物）方面表现出更高效的光催化行为。同样，与未退火的薄膜相比，在 1000 °C 的氮气气氛中退火并添加石墨烯的 ZnO 薄膜表现更好。XRD 分析证实，氧化锌薄膜的预热处理会促进再结晶，但对光催化性能的改善影响较小。石墨烯附着在薄膜上被认为是提高光催化性能的原因。拉曼分析表明，与未退火薄膜相比，退火后 ZnO 薄膜上的石墨烯覆盖面积增加了两倍，而未退火薄膜上的石墨烯层更高。本研究的结果表明，退火后的氧化锌薄膜能与石墨烯形成更好的附着，从而使石墨烯覆盖面积更大，多层膜更少，有效提高了复合结构的光催化活性。
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